For example, in manufacturing a semiconductor device, processes such as, for example, a deposition process, an oxidation process, a diffusion process, an annealing process, and an etching process are performed on a semiconductor wafer which is an object to be processed. When these processes are performed, a heat treatment apparatus is used which includes a processing container configured to accommodate an object to be processed, and a heater device disposed on an outer circumference side of the processing container to surround the processing container.
The heater device includes, for example, a resistance heating element (heater element), and a cylindrical insulating member provided around the heater element. Specifically, the heater element is disposed on an inner circumference side of the insulating member by being wound, for example, in a spiral form through a supporting member. The supporting member supports slidably the heater element at a predetermined pitch.
In such a heater device, the heater element is supported slidably with a clearance in relation to the insulating member. However, the heater element is subject to creep strain by being repeatedly used at a high temperature, and its line length is elongated with elapse of time. When an excess length that occurs in the heater element due to the elongation of the line length of the heater element (hereinafter, referred to as “permanent elongation”) is bent and deformed, axially adjacent turns of the heater element come in contact with each other, thereby causing a short-circuiting. Also, the heater element may be broken due to stress caused by deformation, such as, for example, thermal expansion and contraction, occurring according to heating and cooling of the heater element, as well as permanent elongation.
In order to solve these problems, Japanese Patent Laid-Open No. 2013-16502 discloses a heater device in which a heater element is allowed to move radially according to thermal expansion and contraction of the heater element but is suppressed from moving downward.